Ink composition, inkjet recording method, printed material, and process for producing lithographic printing plate

Abstract

An ink composition is provided that includes (A) an N-vinyllactam, (B) a polymerization initiator, and (C) a basic compound, the content of the N-vinyllactam (A) being at least 15 wt % of the total weight of the ink composition. There is also provided an inkjet recording method that includes (a 1 ) a step of discharging the ink composition onto a recording medium, and (b 1 ) a step of curing the ink composition by irradiating the discharged ink composition with actinic radiation. Furthermore, a printed material obtained using the ink composition is provided. Moreover, there is provided a process for producing a lithographic printing plate that includes (a 2 ) a step of discharging the ink composition onto a hydrophilic support, and (b 2 ) a step of curing the ink composition by irradiating the discharged ink composition with actinic radiation so as to form a hydrophobic image on the hydrophilic support by curing the ink composition.

1. An ink composition for inkjet recording comprising:
 (A) an N-vinyllactam; 
 (B) a polymerization initiator; 
 (C) a basic compound; and 
 (E) a basic dispersant; 
 wherein the content of the N-vinyllactam (A) is at least 15 wt % but no greater than 40% of the total weight of the ink composition, 
 the viscosity of the ink composition at 25° C. is 3 to 50 mPa·s, 
 the basic compound is an organic amine compound having a polymerizable group is at least one selected from the group consisting of N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, and an aminoacrylate in which a polyfunctional acrylate monomer or polyester acrylate is modified with an amine, 
 the basic dispersant is a polymeric dispersant having an amine value that is larger than its acid value, 
 the difference between the acid value and the amine value of the polymeric dispersant is at least 5 mg KOH/g, and 
 the polymerization initiator (B) consists of a radical polymerization initiator. 
 
     
     
       2. The ink composition according to  claim 1 , further comprising (D) a colorant and (F) a surfactant. 
     
     
       3. The ink composition according to  claim 1 , wherein the N-vinyllactam is N-vinylcaprolactam. 
     
     
       4. The ink composition according to  claim 1 , wherein the viscosity of the ink composition at 25° C. is 7 to 30 mPa·s. 
     
     
       5. An inkjet recording method comprising:
 (a 1 ) step of discharging the ink composition according to  claim 1  onto a recording, medium; and 
 (b 1 ) a step of curing the ink composition by irradiating the discharged ink composition with actinic radiation. 
 
     
     
       6. The inkjet recording method according to  claim 5 , wherein the actinic radiation is UV radiation having a peak light emission wavelength in the range of 350 to 420 nm and is emitted by a UV radiation-emitting light-emitting diode that gives a maximum illumination intensity on the surface of a recording medium of 10 to 2,000 mW/cm 2 . 
     
     
       7. A process for producing a lithographic printing plate, the process comprising:
 (a 2 ) step of discharging the ink composition according to  claim 1  onto a hydrophilic support; and 
 (b 2 ) a step of curing the ink composition by irradiating the discharged ink composition with actinic radiation so as to form a hydrophobic image on the hydrophilic support by curing the ink composition. 
 
     
     
       8. The ink composition according to  claim 1 , wherein the radical polymerization initiator is an aromatic ketone. 
     
     
       9. The ink composition according to  claim 1 , wherein the ink composition comprises at least three types of radical polymerization initiators. 
     
     
       10. The ink composition according to  claim 1 , wherein the radical polymerization initiator includes at least one type of an acylphosphine compound and at least two types of aromatic ketones.